The impregnation of porous bodies with the catalytic material plays an important roll in the various processes for the production of catalysts.
These materials are frequently present in the form of solutions or suspensions but also can be present in melted form, which materials then must be applied to the porous carrier.
Besides natural materials such as pumice, kieselguhr, asbestos, kaolin, and magnesia, there are now used above all synthetic materials such as, e.g. activated carbon, silica gel, silicates, zeolites, various metals, and metal oxides and even carbides and nitrides.
Such processes, however, can no longer be carried out if the contact carrier is present in the form of tubes which should be coated internally. Thus for example, in the so-called BMA process for the production of hydrocyanic acid, the contact is prepared according to the method described in German Pat. No. 919,768.
In spite of the good distribution of the catalyst liquid through oscillations and turnings of the contact tube, see the example in the above-mentioned patent, the production of a homogeneous internal layer continuously presents great difficulties since the surface of the porous body naturally is not so homogeneous that no cavities or raised portions occur and therewith there is impaired the adhesion of the catalyst on the contact. Through these nonuniformities the distribution of the catalyst and therewith its effect inside the tube differ, entirely apart from the fact that the coating itself is very consumptive of work and time.
The object of the present process is to prepare an internal coating of contact tubes with catalyst that requires the least possible manual labor and solves the above-described problem in a simple manner.